1. Field of the Invention
This invention relates to electronic circuits, and more particularly, to circuits for programming and reading fuses in integrated circuits.
2. Description of the Related Art
Integrated circuits, such as processor, often times use fuses to store configuration information. For example, during the final phases of manufacturing of a processor, various fuses may be programmed to determine the processor configuration. This configuration may vary according to the type of system in which the processor is to be used (e.g., one configuration for a laptop, another configuration for a desktop), which interfaces are to be activated, the frequency of the core clock, and so forth.
During initialization of the integrated circuit, the configuration information is read and used to configure it for operation. More particularly, fuses are read to determine which ones are programmed (i.e. ‘blown’) and which ones are not programmed (i.e. not ‘blown’). The integrated circuit is then configured for operation based on which fuses are programmed and which are not.
In order to program a fuse, a circuit coupled thereto may draw a sufficient amount of current through the fuse in order to cause the fuse to effectively form an open circuit by increasing its resistance significantly. After the fuse has been programmed, another circuit coupled thereto may sense the state of the fuse upon startup of the integrated circuit.